Catheters are widely used by the medical profession for a variety of purposes and procedures. For example, catheters are commonly used in the treatment of atherosclerotic lesions or stenoses formed on the interior walls of the arteries. One procedure developed for the treatment of such lesions or stenoses is coronary angioplasty. The most commonly practiced angioplasty procedure is known as percutaneous transluminal coronary angioplasty, or PTCA. According to this procedure, a balloon located at the distal end of a dilatation catheter is guided through the patient's vasculature and positioned within the stenosis. The balloon is then inflated such that it dilates the stenosis and opens the restricted area of the artery. After a short period of time, the balloon is deflated and removed from the patient's vasculature.
Typically, the dilatation catheter is maneuvered through the patient's vasculature with the use of a flexible guidewire having a diameter of approximately 0.018 to 0.015 inches and a length of about 180 centimeters. The distal end of the guidewire is extremely flexible so that it may be routed through the convoluted arterial pathway to the site of the stenosis. After the distal portion of the guidewire is positioned across the stenosis, a dilatation catheter having a lumen adapted to receive the guidewire is advanced over the guidewire until the balloon is positioned within the stenosis.
During a catheterization procedure, it may be necessary to thread a catheter on or off an indwelling guidewire, or exchange an indwelling catheter with another catheter over an indwelling guidewire. When using a conventional over-the-wire catheter having a guidewire lumen extending throughout the length of the catheter, it is necessary to extend the guidewire outside the patient's body a sufficient distance to enable the catheter to be threaded on the guidewire without disturbing the position of the distal end of the guidewire within the stenosis. Because of the difficulty in managing such a long guidewire, the additional length of guidewire needed is typically provided through the use of a guidewire extension which is temporarily "linked" or attached to the proximal end of the guidewire. Once the catheter has been threaded onto the guidewire extension and advanced over the guidewire through the patient's vasculature, the guidewire extension may be detached from the guidewire.
Alternatively, an exchange wire on the order of 300 centimeters may be guided through the patient's vasculature such that its distal portion is positioned across the stenosis. The catheter may then be advanced over the exchange wire without disturbing the position of the distal end of the wire. After the balloon located at the distal end of the catheter is positioned within the stenosis, the exchange wire may be removed from the guidewire lumen and replaced with a shorter, easier to handle guidewire.
A number of alternative dilatation catheter designs have been developed in an attempt to eliminate the need to use guidewire extensions or exchange wires. One such catheter design is disclosed in U.S. Pat. No. 4,988,356 issued to Crittenden et al. This catheter and guidewire exchange system includes a catheter shaft having a slit which extends longitudinally between the proximal end and the distal end of the catheter and radially from the catheter shaft outside surface to the guidewire lumen. A guide member slidably coupled to the catheter shaft functions to open the slit such that the guidewire may extend transversely into or out of the slit at any location along the length of the slit. When using this system, the guidewire is maneuvered through the patient's vascular system such that the distal end of the guidewire is positioned across the treatment site. With the guide member positioned near the distal end of the catheter, the proximal end of the guidewire is threaded into the guidewire lumen opening at the distal end of the catheter and through the guide member such that the proximal end of the guidewire protrudes out the proximal end of the guide member. By securing the guide member and the proximal end of the guidewire in a fixed position, the catheter may then be transported over the guidewire by advancing the catheter toward the guide member. In doing so, the guide member slides down the length of the catheter and spreads the slit such that the guidewire lumen envelops the guidewire as the catheter is advanced into the patient's vasculature. The catheter may be advanced over the guidewire in this manner until the distal end of the catheter having the inflation balloon is positioned within the stenosis and essentially the entire length of the guidewire is encompassed within the guidewire lumen.
Furthermore, the indwelling catheter may be exchanged with another catheter by reversing the operation described above. To this end, the indwelling catheter may be removed by holding the proximal end of the guidewire and the guide member in a fixed position and withdrawing the proximal end of the catheter from the patient. When the catheter has been withdrawn to the point where the guide member has reached the distal end of the slit, the portion of the catheter over the guidewire is of a sufficiently short length that the catheter may pass over the proximal end of the guidewire without disturbing the position of the guidewire within the patient. After the catheter has been removed, another catheter fitted with a guide member and a longitudinal slit may be threaded onto the guidewire and advanced over the guidewire in the same manner described above with regard to the original catheter.
Another catheter design having a slitted catheter shaft in communication with a guidewire lumen is disclosed in U.S. Pat. No. 4,748,982 issued to Horzewski et al. This catheter design includes a guidewire lumen which extends along only a short portion of the distal end of the catheter. Accordingly, when the catheter is advanced over the guidewire, the guidewire is located outside the catheter except for the short segment which passes through the guidewire lumen at the distal end of the catheter. As disclosed in Horzewski et al., the catheter shaft defining the guidewire lumen includes a longitudinal slit which extends from the proximal end of the guidewire lumen toward the distal end of the guidewire lumen. This slit facilitates the exchange of catheters by shortening the length over which the guidewire extends through the guidewire lumen during removal of the catheter. When it is desired to exchange the indwelling catheter with another catheter, the catheter is withdrawn from the patient until the proximal end of the guidewire lumen extends outside the patient. From this point as the catheter is further withdrawn from the patient, the guidewire can be pulled out through the slit until the catheter has been withdrawn to the point of the termination of the slit near the distal end of the guidewire lumen. The portion of the catheter remaining over the guidewire is of sufficiently short length that it can be removed over the proximal end of the guidewire without disturbing the position of the distal end of the guidewire within the patient.
Despite these advantages slitted catheters have been known to fail to adequately contain the guidewire within the guidewire lumen during normal operation. More particularly, as the catheter is advanced over the guidewire through the patient's convoluted vasculature it is often bent such that the catheter slit buckles and creates an opening through which the guidewire may protrude. Should the guidewire protrude through the slit it may possibly cause trauma to the interior walls of the arteries. In addition, should the guidewire protrude from and subsequently become pinched within the slit, the distal end of the guidewire may be pulled out of or pushed beyond the treatment site, thus complicating the procedure and requiring repositioning within the patient's vasculature.